Blow open, blow closed circuit breaker system



June 24, 1952 13, woo 2,601,483

BLOW OPEN, BLOW CLOSED CIRCUIT BREAKER SYSTEM Original Filed March 16, 1948 4 Sheets-Sheet l June 24, 1952 Original Filed March 16, 1948 J. D. WOOD 2,601,483

BLOW OPEN, BLOW CLOSED CIRCUIT BREAKER SYSTEM 4 Sheets-Sheet 2:

F3 -d2 w-dlf: m .l "1 35; Ta -=1? A36 141140 192 140 "-187 216 127 194 I: j i 186 l It 9- g If} 116 131 133 a r L k 112 y 4 v INVENTOR. JUJEBQ'DWOOD June 24, 1952 J. D. WOOD 2,601,483

BLOW OPEN, BLOW CLOSED CIRCUIT BREAKER SYSTEM Original Filed March 16, 1948 4 Sheets-Sheet a INVENTOR. JOSEPH Z7. WOOD June 24, 1952 J. D. WOOD 2,601,483

BLOW OPEN, BLOW CLOSED CIRCUIT BREAKER SYSTEM Original Filed March 16, 1948 4 Sheets-Sheet 4 J'OJEPHD WOOD WMIl M Patented June 24, 1952 BLOW OPEN, BLOW CLOSED CIRCUIT 3 BREAKER SYSTEM- Joseph D. Wood, Strafl'ord Village, Pa., assignor to I-T-E Circuit Breaker Company, Philadelphia, Pa.,' a corporation of Pennsylvania Original application March 16, 1948, Serial No. 15,183. Divided and this application vQctober 27,1948, Serial No. 56,755

.9 Claims. (015200-97) This application i a division of my application Serial No. 15,183, filed March 1-6, 1948 now abandoned. a

My invention relates to a novel sequential trip system, and more particularly relates to a sequential trip system in which circuit breakers have time differentials from each other of the order of cycles inrespon-se to short circuit current conditions and have time differentials from each other of the order of seconds in response to overload fault conditions in-the circuit being protected. a I v In such systems it is desirable-that the contacts of the circuit breakers be soconstructed that normally during the GlOSil'lg operation of the breaker it be supplied with a blow-closed effect, i. e., to have'the magnetic fields induced by the currents in the controlled circuit tend to drive the contacts closed. This ensures good contact on closing and is especially desirable where breakers may be closed against excessive currents or short circuit conditions.

Under such circumstances, the contacts are sufficiently closed to enable'relatching of the contacts before tripping occurs inresponse to such short circuit conditions and thus avoids chatter ing or freezing at the contacts due to poor contact engagement during closing.

While it is thus desirable to have a blowclos'ed effect during closing in order to ensure complete latching in response to the fault currents, it is at the same time desirable to retain the effector a blow-open action during the tripping of the breaker, i..e.,.an action in which When the breaker is tripped in response to a'fault current, the electromagnetic fields set up by such currents function in a direction to assist in driving the contacts to disengagement.

In accordance with my. novel sequential trip system, I accordingly provide circuit breakers in such a system having time delaysboth forshort periods of the order "of cycles for. currents upto 1.0 and long periods of the order of seconds for overloads which are individual to each of the breakers and differ from'each other-tin the'short circuit current ranges by. cycles of separation and in the long current by seconds-ofseparation and which are provided with what I above define as a blow-closed, blow-open action.

Accordingly, an objectof my invention is to provide a novel sequentialtrip mechanism in which the breakers are eachzprovided with blowclosed, blow-open mechanisms.

Another object of my invention is .to provide a novel sequential trip *system in. which each of 2 the circuitbreakers is constructed so that the electromagnetic fields set up assist with the circuit breaker in closing and also assistin the openingof the contacts in response to fault currents.

The foregoingand' many other-objects. of my invention will become app'arent fr'om the detailed description of the figures whichfollows, in which Figure '1' is aschem'atic'illustration of one form of circuit breaker which may be employed in my novel sequential trip system. Y 1

Figure? is a circuit diagram of a system in which said circuit breakers may be used.

Figure 3 are curves showing th e time current responses of circuit breakers" employed in my system.

Figure 4 is a schematic illustration of another form of breaker which may be" used in my system showingthe breaker in closed position.

Figure 4a is a'schema'tic illustration of the distribution of forces.

Figure 5 shows'th'esame breaker-'infull open position.

Figure 6 shows the breaker in pro-set position ready to be reclosed. U

Referring now to the figures, I have here shown my novel ci'rcuitbreaker 'I ll which is so arranged that during the closing movement and just as the contacts engage, but before theyhave fully engaged, the current loopthrough the elements provides a blow-closed effect. When'thecircuitbreaker is tripped, the elements are so arranged that the current loop provides a blow-open effect.

The circuit breaker l0 is supported inany suitable; manneron a backpanel I I carrying additional supporting brackets, not'sh'own, to support the various pivot pins hereinafter described.

..The back panel Ito'arries an upper back connection stud l5 and a lower back connection stud 16, mounted in any suitable insulators H5 and I16. The upper back connection stud 15 carries at the end thereof a stationary contact structure 1?. Movable contact arm 25 carrying movable contact 25 and are horn 2'!- is pivotally mounted on the pin 28 which passes through the arcuate horizontally extending slot 29 in extension 3 I. of the lower back connection stud [6.

Further. details of contactarm 25 are shown in. Figure la of application Serial 'No." 720,561, filed January '7, 1947.

The current path established when the confacts are closed is thus from the "upper back conneotion. stud. .l 5 to the stationary contact structure ILth'enthrbugh movable contact 26 and 3 movable contact arm 25 to the extension 31 of the lower back connection stud i and then to the lower back connection stud l5.

It will thus be seen that when the contacts are closed, a U-shaped current loop is established with the contact elements ll25 at one of the bends or corners of the loop.

The movable contact 25 is held closed during the operation of the circuit breaker by the toggle 52, one link 53 of which is connected to the pin 50 on contact arm 25, the opposite end of the link 53 being connected to the knee pin 55 of the toggle 52.

The other link 54 of the toggle 52 is connected at one end to the knee pin 55 and is pivoted at the other end on the stationary pin 51. Link 54 has a downward extension 52 which with link 54 forms a bell crank lever 5452. Roller 63 secured at the end of link 52 is engaged in detent 54 of latch 55.

Trip magnet "H is energized in accordance with current conditions in the main circuit through the current transformer 73 in the main circuit. Armature l2 of magnet H is connected to a short time delay device 14 and through spring 5| to a long time delay 14. Both the long and short time delay are here shown schematically and may be as shown in Patent 2,439,165 assigned to the assignee of the present application.

When prolonged overload current conditions of the order shown in the upper portions A to D of curves 1-4 obtains, the armature is operated against the delaying action of the long time delay M. When a short circuit condition of the order shown in the lower portions E to H of curves 1-4 obtains, the armature is operated against the delaying action of the short time delay of device 14, all as more specifically described in the aboveidentified patent.

The time delay characteristics of each of the circuit breakers in the system have individual time characteristics, such as shown in curves l-4 of Figure 3. Accordingly, as explained in the above-identified patent, only the circuit breaker nearest the fault will open.

When the overload trip coil ll is energized over a circuit to current transformer operated by short circuit current in the main circuit protected by the circuit breaker, the armature I2 is raised against extension 51 of latch 55 causing the latch 55 to pivot counterclockwise about the stationary pin 88 so that the detent 54 thereof disengages roller 53 and the toggle 52 may break downwardly.

During the closing operation, the possible movement of the toggle upwardly through center is prevented by the cross-bar or stop above the knee pin 55. When the toggle 52 has broken downwardly, thus permitting the contact to be forced open by the blow-open effect, the knee pin 55 drops and roller 53 rises. Roller 63 is connected to the link T5. Link 15 is provided at its outer left-hand end with a slot 15 in which rides the pin 'l'l. Pin 77 is connected to the upper end of the bell crank lever latch 18 which is pivoted on the pin 19.

Latch '58 has a detent 88 which engages roller 8| on the closing arm 82. Arm 82 is pivotally mounted on the pin 53 and is biased toward the right into clockwise movement by the compression spring 84.

When now the roller 53 rises up toward the left, on opening of the contacts, the link '15 is driven to the left rapidly and when the end 15a of the slot 7-,: strikes pin 11, latch 18 is given a hammer blow in a counterclockwise direction to disengage the detent from roller 8!.

The compression spring 84 is now in a position to drive the arm 82 clockwise around the pivot 83. This results in the movement of the parts to the condition wherein the closing toggle 88 has collapsed, and in which the adjustable stop member 8| at the upper end of the arm 82 strikes the extension 62 of the link 54 rotating link 54-52 in a counterclockwise direction to re-extend the toggle 52 once more and to re-engage the roller 53 in detent 54 of latch 55.

The re-setting or extending of the toggle 52 does not at this time, however, result in closing of the circuit breaker, since pin 85 on arm 82 which is connected to arm 5| moves the arm 5| to the right, thus moving the pin 86 at the lower end of contact arm 25 to the right. This moves the pin 28 of the contact arm 25 to the righthand side of the slot 29 but at the same time pushes the pin 55 over sufficiently so that the contact arm continues to rotate outwardly toward the left around pin 28 which is held by the right-hand end of slot 29. Thus, even though the latches are rc-set, the circuit breaker remains open.

The closing toggle S5 is prevented from breaking upwardly by the stop 95. Toggle comprises a link 93 connected by pin 94 to the closing arm 52 and connected at the other end to the knee pin 95. Link 91 is connected at one end to knee pin 55 and at the other end to the stationary pin 58. Closing solenoid 99 is provided with the armature I00.

Now when the circuit breaker is in the open position with the latches all re-set, the contacts may be closed by energization of the solenoid coil 98. On such energization the armature 100 is raised to extend the toggle 95. When the toggle 85 is thus extended, closing arm 82 is rotated counterclockwise to the left about pin 83. This compresses the spring 84 and moves the arm 82 over to the left until latch 18 engages roller 8| on the arm 82. At the same time the movement of arm 82 to the left pulls the arm 51 to the left, thus pulling on pin 50 and causing the contact arm 25 to rotate in a counterclockwise direction around the pivot pin 50.

Spring 84 is provided only to re-set the toggle 52 and consequently is a relatively light spring so that it does not interfere with the closing of contacts as would be the case where opening springs are used. Thus, the mechanical force needed to close the contact is only necessary to overcome the inertia of the parts and the relatively slight force of the re-setting spring 84.

The contacts are driven home once they are initially engaged by the blow-closed effect below described. In fact, the closing coil and armature, as hereinafter pointed out, are aided by the arrangement of the parts which produce a net blow-closed effect during closing.

Also, the travel which is given to the closing coil and armature I00 need merely be sufiicient to complete the closing operation and no over-travel need be provided to provide any hammer blow or kinetic effect to slam the contacts home, owing to the blow closed effect described below. The parts may thus be made lighter and at the same time, owing to the utilization of the electromagnetic forces to close the contacts rather than sheer mechanical forces or kinetic energy, the parts are more durable.

The operations whereby a blow-closed effect is secured during closing and closed conditions aeonass and ablow-open efiect is secured during tripping will now be described.

In. the position shown in Figure 1 with. the .circuit breaker closed, when ashort circuit current flows through conductor and the fixed and movable contacts l8 and 26 through movable contactarm and backxthrough conductor it, a force is applied to the movablearm 125 which is transferred through pin to link 53 and pin torset'up a force on the bell crank'5' l and 62 which is in a clockwise direction about pin 511.

At this instant, the force is resisted by :the latch 64 engaging pin 63 from driving the .arm 15 to'the left. The overload. relay ll connected in series in the circuit through conductors :125 and [6 described above is energized by this same'overload current andoperates its armature 1-2 toengage the projection -6 rocking the latching lever 'about pin 66 in a counterclockwise direction and disengaging latchBt from pin 63.

The above described 'forces thereupon are free to act and the contact arm '25 is rocked in a counterclockwise direction about the pin 60. It should be noted at this point that the blowopen eifect on the arm '25 described above has a lever arm extending to the pin 60 so that although the resultant force of this blow-open effect is applied at the pin 50, it is this force at pin 56 times the lever arm formed to the -pin-60 which produces the counterclockwise movement of the arm 25.

Upon disengagement of the latch 64 from pin 63, the toggle 52 collapses downwardly, rocking' the bell crank arm 54 and '62 in-a clockwise direction about the pin 51. The movement of thepin 63 to the left as a result of this-operation operates the link 15 to the left until the pin 11 engages the righthand end 16a of the slot 16. Further movement of the pin 63 thereupon rocks the bell crank 18 about its pivot 19 in a counterclockwise direction until the latch disengages the pin 8|.

' Opening springs attached to movable contact arm 39 may be provided to ensure openingat no load.

When now the latch 80 disengages pin -81, the arm 82 is operated clockwise about pin 6-3 under the action of the compression spring 84, collapsing the toggle so that the links 63' and 61 rock downwardly and the knee pin '96 is moved down to engage the armature I00 of the-closing magnet 99.

A further result of the movement of arm 62 is to move the link 6| to the right, Asthe pin 60 of linktl is moved to the right, the contact arm 25 is also carried 'to the right with the pin 28moving in the slot 29 until the pin 28 engages the right-hand end of the slot. During this movement the toggle mechanism 52, including links 53 and 54, have been straightened out to the position shown in Figure. 3 of application Serial No. 720,561, filed January '7, 1947. Movement of the link 54 operates this bell crank about pin 5'! ma counterclockwise direction, thus operating the pin63 and through it the-link 115-to the right until the pin TI is in the intermediateposition of the slot I6.

At this position the :latch 65 which has in the meanwhile been restored to itsroriginal .position as a result of the de-energization of the magnet H re-engages the pin 63 to re-set the toggle mechanism 55 and hold it in the position preparatory for the ire-closing operation.

On ire-closing the holding magnet!!!) is operated, operating its plunger armature upwardly against .the knee pin :96 :and' the latter is raised toward :the stop .55 thus straightening out the knee :toggleto the position :shown in Figure 1.

During this operation .the link :03 is :moved' to the leitroperating the arm i82 iinua :counterclockwise direction :about pin :63 untilrtheepin 32 moves over the latch 88: .and zre sets itself in engagement with the latch. The movem'entiof thearm 82 in a counterclockwise direction opcrates through. pin .85. to move link 6| :to :the left. As aresult, theipin fionowrotates the-iarm 25 about. .pin .50 .whichtis now fixed by thereengaged toggle 1512 until the .contacts ire-engage.

If new the contacts closenon a short circuit during the instant .of engagement, the :magnetic. forces set up by the short circuit :currents will produceia magnetic aotioniabout' the pin-50.. The portion of the magnetic :forces in thessectorififi between pin50 andrthe engaging contactsawould tend to drive'thamovablearm in acounterclockwise direction "about the .pin 15.0 .At :thessame' time the magnetic forces below ithe :pin :50 will. operate on the link extending from 5.0 to 50, including :the 1 section '40 between :pin :GDt-and-z pin and the :section 39 between the :pin .26zand pivot pin 55 to drive the movable arm ;25 in ;-a clockwise direction about pin 5.0.

Since the I closing pivot is ;pin :50, the :magnetic. forces on opposite :sides of pin 550 on sections 39 and AI of arm 25 at -least cancel eachaother out so that the mechanical closing ,iforce :meets no opposition. With section 39 of arm;2,5 even slightly greater than the distance from pivot 55 to contact 26, a net .blowclosedtactionmccurs.

As soon, however, as'th'e toggle. .52 iisihroken by the disengagement of the latch 6'4 from-pin 63 in response .tothe fault,cmrentszaszidescribed above, the pin .50 ceases to be :fixed .onpivo't point for the movable arm 25 :andthepivotzpoint for the movable .arm now is transferred to the pin 60 as'described above.

Accordingly a blow-open action on the movable arm 25' is produced extending .over-ithecentire length of .the arm '25 from "the :engaging contacts to the pin 60,1thus ensuring'highr-speedz disengagement of the contacts.

In Figures :4to-6, I havev shown. azmodifieil form of circuit breaker which :may be employed my novel system. In this system, a ;circultbreaker H0 is shown arranged so that during the closing movement and :just "as thercontacts engage, but before they have fully engaged, the current loop through the elements provides :a blow-closed effect; When "the circuit .breaker is tripped, the elements are so :arranged that the current loop provides a blow-openqeffiect and the contacts are of the blow-closed construction; The circuit breaker H0 is supported in :amy

suitable manner on :a panel 'I H, carrying :the additional supporting bracket M2- and ;fr.ont panel H3.

The back panel I H carriesran upper back;connection stud 215 and. a lower back connection stud 2l6, mounted in any suitable insulator H15 and H6. The upper back connection stud 215 carries at the end thereof a stationary contact housing H1 comprising an :arcing :contact .116

that the electromagnetic force due to high short circuit current will tend to force them into better contact engagement with the moving contact.

The movable contact arm I is a composite linkage member having an upper arm I26 and a lower arm I21 connected by the pin I28. The lower arm I21 is rotatably mounted on the stud I30 connected to the extension I3I of the lower back connection stud 2I6 and is held in current carrying engagement therewith by the friction discs I33. The lower arm I21 is held in current carrying engagement with the upper arm I26 also by friction discs I surrounding the pin I28.

Upper arm I26 has an angular extension I therefrom substantially in the region of the pin I28, the said extension I40 having secured to the outer end thereof at the pin I4I the upper end of the tension spring I42 which tends to bias the upper arm I26 toward the open position. The lower end of tension spring I42 is secured to the lower pin I30. The upper arm I26 carries the movable arcing contact I45 and the movable main contact I46.

The current path established when the contacts are closed is thus from the upper back connection stud 2I5 to the stationary contact structure II1, including the arcing contact H8 and the main contact I I9, then through the movable arcing contact I45 and the movable main contact I46 to the upper arm I26 of the contact arm I25, then through the friction discs I35 and pin I28 to the lower arm I21 of the composite contact arm I25, then through the friction discs I33 and pin I30 to the extension I3I of lower back connection stud 2I6.

It will thus be seen that when the contacts are closed, a U-shaped current loop is established with the contact elements I I8I45 and I ISL-I40 at one of the bends or corners of the loop.

Accordingly, were it not for the specific novel structure of the contact arm I25, a blow-open effect would be seen to result on the contacts when the breaker is in the closed position.

Actually, the contact arm I25 and its associated operating mechanism is so designed that a blow-closed efiect results. This occurs primarily by reason of the fact that the distance from the pin I50 to the pin I30 is greater than the distance from pin I50 to the contacts I46 and I45, and the flexible stationary contacts are of a blow-closed design.

The effect of this difference in length or distance will be obvious from a fuller explanation of the operating mechanism itself and the manner in which it co-acts with the contact arm I25. y

The upper arm I26 of the contact arm I25 is biased toward opening position by the tension spring I42 in the manner previously described, the tension spring I42 causing the arm I28 and its extension I40 to rotate in a clockwise direction when the force which holds the contact arm I26 closed is removed.

Contact arm I25 is held in the closed position by the toggle I 52 comprising links I53 and I54 and the knee pin I55. Link I53 may be of insulating material in some cases. Link I53 is pivotally connected to pin I50 of upper arm I26 and at its opposite end is connected to knee pin I55. Link I54 is connected at one end to pin I55 and at its opposite end is pivoted on the pin I51 mounted between the sides of bracket I which in turn is supported on the front panel II3.

Link I54 has an angular extension I62 so that members I54-I 62 form a bell crank lever around the pin I51. The outer or lower end of extension I62 carries a latch roller I63 which is engaged by the latching detent I64 of the pivoted latch member I65. Latch member I65 is rotatably mounted on the pin I66 carried between the sides of bracket I60.

The latch lever [65 is in the path of movement of the armature I10 of trip coil I1I. Armature I10 is connected to the short time delay device I12 and through spring I13 to the long time delay device I15 of the type shown more fully in Patent 2,439,165. As explained hereinbefore, and also in the above-identified patent, the armature is delayed in its operation for relatively long periods of time of the order of seconds when overload current conditions obtain in the main circuit being protected and is delayed in its operation for relatively short periods of time of the order of cycles when short circuit currents obtain in the main circuit being protected.

When the trip coil I1I is energized in response to predetermined circuit conditions, the armature I10 rotates the latch member I65 in counterclockwise direction to release the latching detent I64 of the latch I65 from the latch roller I63 of the bell crank lever I54I62.

Since the toggle I53--I 55-I 54 is broken slightly upwardly in the closed position of the circuit breaker, the arm I26 may now on release of the latch roller I63 rotate clockwise around the pin I28 breaking the toggle I52 up to the position shown in Figure 5. This movement of the arm I26 in a clockwise direction is in response to the force of the tension spring I42 which therefore acts as the opening spring of the circuit breaker. During this opening stroke of the breaker, it will be noted that the efiect of the electromagnetic forces due to current flowing in the circuit is to hasten the contact opening, thus aiding high speed circuit interruption. This I have called the blow-open effect.

A portion of the link I54 strikes the buffer I14 carried by the front panel H3 and the upward breaking of the toggle I52 and hence the opening movement of contact arm I26 is thereby limited.

The closing arm I which may be of insulating material is connected at one end to the pin I28 and at the opposite end to a pin I8I on the armature I82 of the closing solenoid I83. The armature I 82 is normally biased toward the left by the compression spring I 85 which is seated at one end in the recess I86 of armature I82 and at the opposite end in the recess I81 of the housing I88 for the coil I83. Housing I88 is supported from the front panel Il3.

With the circuit breaker in the open position, the compression spring I85 as seen in Figure 6 has moved the armature I82 fully to the left, thus moving the closing arm I80 and the pin I28 t0 the left and rotating the lower arm I21 of the contact arm I25 counterclockwise around the pin I30.

In the fully closed position of the circuit breaker, (Figure 4) the energization of the closing coil I83 has attracted the armature I82 to the right compressing the spring I85 and pulling the arm I 80 and pin I28 to the right and rotating the lower arm I21 of contact arm I25 clockwise around the pin I30. When the closing movement is completed, the arm I80 is latched in closed position as shown in Figure 4 by the latch roller I90 in the latching detent I9I of the arm I80.

To ensure this movement and to limit the movement of arm I26 during opening, a projection I84 on closing arm I60 is arranged to engage arm I26 in the fully open position and drive it clockwise to the reset position of Figure 6.

Latch roller I90 is supported at the end of the bell crank latching lever I92, which latching lever is rotatably supported on the pin I93 carried by an extension I94 of bracket I60. The upper arm I95 of latching lever I92 is so arranged that during the opening movement of the circuit breaker, that is, when the circuit breaker moves from the position of Figure 4 to the position of Figure 5, the latch roller I63 at the end of arm I54--I62 will strike the upper end I95 of the latch lever I92, as seen in Figure 5, to rotate the latching lever I92 counterclockwise and to move the latch roller I90 out of the latching detent I9I of closing arm I80 so that the closing arm I80 may move to the left in response to the bias of compression spring I85.

Tension spring I96 connected between the arm I95 of the latching lever I92 and extension I91 of the latching lever I65 biases the latching lever I92 toward clockwise rotation and hence toward latching position with respect to arm I80, and at the same time biases the latching lever I65 toward clockwise rotation and interengagement with the latch roller I63. The single spring I96 is thus used to re-set both of the latching levers I65 and I92.

Thus, as previouslydescribed, on a tripping of the circuit breaker, the armature I'I'0 rotates latch lever I65 counterclockwise to release the latch roller I63 and to permit the toggle I52 to break upwardly so that the arm I26 mayrotate clockwise toward opening position in response to the bias of spring I42. This is the initial step which occurs during tripping and is shown in Figure 5.

As the toggle I52 breaks upwardly, roller I69 strikes the upper arm I95 of the latching lever I92, rotating the latching lever I92 counterclockwise and lifting the latch roller I90 out of the latching detent I9I. The arm I39 is now free to move in response to the bias of the compression spring I85 and moves to the left carrying. the pin I28 with it and rotating the lower arm- I2-I of the contact arm I25 counterclockwise. This moves the lower end of arm I26 to the left taking with it the pin I50 and the link I53.

The latch roller I90 of the latch member I192 rides on the upper surface of the closing arm I80 as shown in Figure 6. Latches are thus reset preparatory to closing the breaker.

The re-set of this mechanism brings the'movable contacts I45 and I46 nearer the stationary contacts II8I I9 than they were in the tripped position (Figure and thus reduces the-travel required to close them.

In the closing operation, the energization of the closing coil I83 attracts the armature I82 to the right against the bias of compression.

spring I85 pulling the arm I80 to-the right and hence rocking the pin I28 and the lower arm I2'Iclockwise about pivot I30. This same movement of pin I28 will rock the upper arm- I26 counterclockwise about pin I50 since the pin I50, except for a slight upward movement to allow for the; are formed by pin I28 in its clockwise movement, is now substantially a fixed pivot owing to the fact that the toggle I52 is restrained from breaking upwardly by engagement of latch elements I63 and I64.

Accordingly, the upper arm I26 now rotates counterclockwise around' the pin I59 as the arm I80 is drawn to the right and as the elements move from the position of Figure 6 to the closed position of Figure 4. When the fully closed position is reached, the latch roller I90 drops into the latching detent I9I of the closing arm I and the circuit breaker is latched closed.

Examining the first operation of closing the circuit breaker, that is, the movement of the elements between the positions of Figures 6 and 4, it will be seen that movement of the arm I80 to the right rotates lower arm I21 clockwise around its pivot I30 and the upper arm I26 counterclockwise around its pivot I50 until the arms (which rotate with respect to each other about the pins I28) are substantially straight and the circuit breaker contacts engage.

The magnetic forces induced by current in the loop from back connection stud 2'I5 through contacts Hi9, I46, arm I25 and lower stud 2I6 tends to rock arm I21 about pivot I30 in a clockwise direction. This force is transmitted through pin I28 to the arm I26 as a force tending' to rock arm I26 about pin I50 in a counter.- clockwise direction. A second effect of the electromagnetic force is to directly apply a moment of rotation against the lower portion of arm I26 from. pin I50 to pin I28 which tends to drive arm I26 in a counterclockwise direction. These two moments, the moment of rotation transferred through arm I21, and that directly applied to the lower part of arm I26, are accumulative and counterclockwise.

A third moment of rotation is applied by the integrated force due 'to the electromagnetic action. of the upper part of arm I26 from pivot I50 to contact II9. This moment of rotation tends to rotate the arm I26 in a clockwise direction. It will be obvious from an examination of the proportional lengths of the arms involved that the sum of the movements about pin I50 in a counterclockwise direction are greater than the moment of rotation about pin I50 in a clockwise direction so that the resultant moment is one which drives the contacts into firmer engagement while the contacts are closed. This is called a blow-closed effect. An analysis of these forces is shown in Figure 4a.

The condition for equilibrium where all forces will be balanced out and no force will be imposed on the closing link I80 is If however,

as d4 then the electromagnetic forces due to current flowing in the circuit will help close the contacts and high speed positive closing will be secured dueto this blow closed eifect.

This current loop, as previously pointed out, will be established just as the contacts engage, but before they are in full engagement and hence before the latch roller I is forced by the spring I96 into latching detent I9I.

With armature I82 at the end of its stroke at about this time, the net blow-closed effect achieved assists the closing coil I83 in completing the closing action. The contacts are forced home by this net blow-closed effect until the latch roller I99 enters the latching detent I9I when the contacts are secured in position.

Accordingly, the closing coil I83 and armature I82 need only have sufficient force to extend the tension spring I42 and move the mechanical parts associated with the contact. They need not be designed to overcome any blow-open effect.

In fact, the closing coil and armature, as above pointed out, are aided by the arrangement of the parts which produce a net blow-closed effect during closing.

Also, the travel which is given to the closing coil and armature I82 need merely be suiiicient to complete the closing operation and no overtravel need be provided to provide any hammer blow or kinetic effect to slam the contacts home. The parts may thus be made lighter and at the same time, owing to the utilization of the electromagnetic forces to close the contacts rather than sheer mechanical force or kinetic energy, the parts are more durable.

My novel device is also so arranged, however, that during the opening of the circuit breaker, a net blow-open effect is achieved. As will be seen from a comparison of Figures 4 and 5, when the circuit breaker is tripped, the toggle I52 first breaks upwardly and the contact arm I26 rotates clockwise in response to the tension of tension spring 42; and it is only after the toggle I52 has broken upwardly that its roller I63 can release the latch I92 to permit the arm I80 to move.

Consequently, at the instant of tripping, the pin I28 is efiectively a stationary pin. Accordingly, during opening arm I26 rotates about at I28 in a clockwise direction. The magnetic forces set up a moment of rotation which is an integrated force between pin I28 and contact II5 multiplied by half the distance between the points. This moment of rotation is also clockwise and drives the contacts open. This is the blow-open efiect.

Accordingly, the blow-open effect at the bend or corner of the U at which the contacts are located can exercise its full force and the tripping operation initiated by the opening spring I42 is substantially aided by t .e blow-open effect.

By this means, therefore, the single composite contact arm I25 is so arranged that it utilizes the electromagnetic forces of high fault currents to assist in closing the circuit breaker where the circuit breaker is to be closed on such high fault currents, and also utilizes the same electroand magnetomotive effects of the high fault currents to speed up the tripping of the circuit breaker when the tripping operation occurs.

The same contact arm I25 is thereby utilized as a blow-closed contact arm during the closing operation of the circuit breaker and a blowopen contact arm during a tripping operation of the circuit breaker.

I claim:

1. Tripping mechanism for a circuit breaker having a movable contact carrying arm and a cooperating contact, a first and second pivot for said movable arm, electromagnetic means for controlling said movable arm about said first pivot to eiiect disengagement of said contacts, a long time delay mechanism for varying the controlling action of said electromagnetic means in the event that said electromagnetic means is energized by overload conditions to effect a delay in the disengagement of said contacts for a relatively long time of the order of seconds, a short time delay means for varying the controlling action cf said electromagnetic means in the event said electromagnetic means is energized by short circuit fault currents to effeet a delay in the disengagement of said contacts for a relatively short period of time of the order of cycles, and means operating said movable arm about said second pivot to effect engagement of said contacts.

2. Tripping mechanism for a circuit breaker having a movable contact carrying arm and a cooperating contact, a first and second pivot for said movable arm, a spring biasing said movable arm to disengaged position, a latch for normally latching said movable arm in contact engagement against the action of said spring electromagnetic means for tripping said latch to permit movement of said movable arm about said first pivot to disengage said contacts, a long time delay mechanism in operative relation with said electromagnetic means for varying the trip time of said latch a long time of the order of seconds in the event that said electromagnetic means is energized by predetermined overload current conditions and a short time delay means in operative relation with said electromagnetic means for varying the trip time of said latch a short time of the order of cycles when said electromagnetic means is energized by short circuit fault, and means operating said movable arm about said second pivot to effect engagement of said contacts.

3. In a circuit interrupter for connection in an electric circuit, a movable arm carrying a contact, a cooperating contact, means for operating said movable arm to eifect engagement between the contact carried thereby and said cooperating contact, a first pivot, said movable arm being mounted on said pivot for movement about said pivot, the distance from said pivot to the contact carried on said movable arm being less than the distance from said pivot to the end of said arm opposite said contact carried by said arm, said arm and its contact and cooperating contact forming with the electric circuit in which said interrupter is connected a loop circuit, means for operating said movable arm about said first pivot to effect engagement of said contacts, a second pivot, electromagnetic means responsive to the electrical conditions in said circuit, means controlled by said electromagnet for operating said movable arm about said second pivot for effecting disengagement of said contacts, time delay mechanism associated with said last mentioned means for effecting delay in the disengagement of said contacts.

4. In a circuit interrupter for connection in an electric circuit, a movable arm carrying a contact, a cooperating contact, means for operating said movable arm to eifect engagement between the contact carried thereby and said cooperating contact, a first pivot, said movable arm being mounted on said pivot for movement about said pivot, the distance from said pivot to the contact carried on said movable arm being less than the distance from said pivot to the end of said arm opposite said contact carried by said arm, said arm and its contact and cooperating contact forming with the electric circuit in which said interrupter is to be connected a loop circuit, means for operating said movable arm about said first pivot to effect engagement of said contacts, a second pivot, electromagnetic means responsive to the electrical conditions in said circuit, means controlled by said electromagnet for operating said movable arm about said second pivot for effecting disengagement of said contacts, time delay mechanism associated with said last mentioned means for efiecting deacornee 1&3 lay'in" the disengagementof said. contacts, said delay being of the order of seconds for predetermined currents and of the order of. cycles for'predeterm-inedi currents of greater amplitude than said first mentioned predetermined currents.

5. Inna circuit interrupter for connection in an electric circuit, a movable arm carrying a contact, a cooperating contact, means for operat ing said movable arm to efiect engagement between the contact carried thereby and said cooperating contact, a first pivot, said movable arm being mounted on said pivot for movement aboutsaid pivot, the distance from said pivot to the contact carried on said movable arm being less than the distance from said pivot to the end of said arm opposite said contact carried by said arm, said arm and its contact and cooperating contact forming With the electric circuitin which said interrupter is connected a loop circuit, means for operatingsaid movable arm' about said first pivot to effect engagement of said contacts, a-second-pivot, the distance from-said second pivot to the nearest turn in said loop being less than from said second pivot to said cooperating contact, electromagnetic means responsive to the electrical conditions in said circuit, means controlled by said electromagnet for operating said movable arm about said second pivot for effecting disengagement of said contacts, time delay mechanism associated with said last mentioned means for efiecting delay in the disengagement of said contacts, said delay being of the order of seconds for predetermined currents and of the order of cycles for predetermined currents of greater amplitude than said first mentioned predetermined currents.

6. A circuit breaker for protecting an electrical circuit having terminals for connection to a circuit to be protected and having a pair of cooperable contacts, a contact carrying arm for carrying one of said cooperable contacts into and out of engagement with the other of said cooperable contacts, a closing mechanism connected to said contact carrying arm mechanism, a first latch for said closing mechanism operable after said cooperable contacts have been moved to engagement and then moved further to tight contact engagement for latching said contacts into tight engagement, a second latch for said movable contact carrying arm, a trip mechanism responsive to fault currents for releasing said second latch to permit movement of said contact carrying arm to effect disengagement of said contacts, a time delay for retarding the time of operation of said trip mechanism, said cooperable contacts forming with said movable contact carrying arm and said terminals a loop electrical circuit setting up electromagnetic forces applied to said movable contact carrying arm, and a construction for said movable con tact carrying arm for applying said electromagnetic forces to said arm in a direction to assist said closing mechanism in effecting contact engagement of said cooperable contacts until said first latch is operated and for applying said electromagnetic forces to said arm in a direction to drive said contacts apart after said first latch is operated.

'7. A circuit breaker for protecting an electrical circuit having terminals for connection to a circuit to be protected and having a pair of cooperable contacts, a contact carrying arm for carrying one of said cocperable contacts into and out of engagement with the other of said cooper- Y Li) able contacts, a closing mechanism connected to said contact carrying arm' mechanism, ,afirst latch for said closing mechanism operable after said cooper-able contactslhave been moved toen- 'agement and then moved further to tight contact engagement for latching said contactsinto tight: engagement, a second latch for said movable contact carrying arm, a trip mechanism responsive to fault currents for releasing said second latch to permit movement of said contact carrying arm to-effect disengagement of said contacts, a time delay for retarding the time ofoperation of said trip mechanism, said cooperable contacts forming with-said movable contact carryingarm and said terminalsa loopelectrical circuit setting up electromagnetic forces applied to said movable contact carrying arm, and a constructionforsaid movable contact carrying arm for applying said electromagnetic forces to said arm in a direction to assist said closing mechanism inefiecting contact engagement of said cooperable contacts until said first latch is operated and for applying said electromagnetic forces to said arm in a direction to drive said contacts apart after said first latch is operated, said construction of said arm comprising a first pivotal connection from said arm to said first closing mechanism latch and a second pivotal connection to said second latch.

8. A circuit breaker for protecting an electrical circuit having terminals for connection to a circuit to be protected and having a pair of cocperable contacts, a contact carrying arm for carrying one of said cooperable contacts into and out of engagement with the other of said 00- operable contacts, a closing mechanism connected to said contact carrying arm mechanism, a first latch for said closing mechanism operable after said cooperable contacts have been moved to engagement and then moved further to tight contact engagement for latching said contacts into tight engagement, a second latch for said movable contact carrying arm, a trip mechanism responsive to fault currents for releasing said second latch to permit movement of said contact carrying arm to effect disengagement of said contacts, a time delay for retarding the time of operation of said trip mechanism, said cooperable contacts forming with said movable contact carrying arm and said terminals a loop electrical circuit setting up electromagnetic forces applied to said movable contact carrying arm, and a construction for said movable contact carrying arm for applying said electromagnetic forces to said arm in a direction to assist said closing mechanism in effecting contact engagement of said cooperable contacts until said first latch is operated and for applying said electromagnetic forces to said arm in a direction to drive said contacts apart after said first latch is operated, said construction of said arm comprising a first pivotal connection from said arm to said closing mechanism latch and a second pivotal connection to said second latch, the distance from said second pivotal connection to said cooperable contacts being less than the distance from said second pivotal connection to the terminal connection. of said arm.

9. A circuit breaker for protecting an electrical circuit having terminals for connection to a circuit to be protected and having a pair of cooperable contacts, a contact carrying arm for carrying one of said cooperable contacts into and out of engagement with the other of said cooperable contacts, a closing mechanism connected to said contact carrying arm mechanism, a first latch for said closing mechanism operable after said cooperable contacts have been moved to engagement and then moved further to tight contact engagement for latching said contacts into tight engagement, a second latch for said movable contact carrying arm, a trip mechanism responsive to fault currents for releasing said second latch to permit movement of said contact carrying arm to effect disengagement of said contacts, a time delay for retarding the time of operation of said trip mechanism, said cooperable contacts forming with said movable contact carrying arm and said terminals a loop electrical circuit setting up electromagnetic forces applied to said movable contact carrying arm, and a construction for said movable contact carrying arm for applying said electromagnetic forces to said arm in a direction to assist said closin mechanism in effecting contact engagement of said cooperable contacts until said first latch is operated and for applying said electromagnetic forces to said arm in a direction to drive said REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,560,440 Tritle Nov. 3, 1925 2,025,697 Baker Dec. 24, 1935 2,186,251 Lindstrom Jan. 9, 1940 2,275,891 Cox Mar. 10, 1942 2,283,748 Mathieu May 10, 1942 

